This invention relates to rupture disk assemblies and, more particularly, but not by way of limitation, to apparatus and method for preventing fragmentation of a rupture disk during rupture of the rupture disk.
A large variety of safety pressure relieving devices of the rupture disk type have been developed and used. Generally, these devices include a rupture disk supported between a pair of complementary supporting members or flanges which are connected to a relief connection in a vessel or system containing fluid pressure. When the fluid pressure within the vessel or system exceeds the design rupture pressure of the disk, the disk ruptures causing fluid pressure to be relieved from the vessel or system through the ruptured disk.
The rupture disks which have been previously used have taken various forms and have included one or more parts. For example, flat rupture disks, rupture disks including domed or concave-convex central portions, and composites of such disks and other components such as vacuum supports, modular support assemblies, cutting members, etc. have all been used. Rupture disks with concave-convex central portions in which the concave side of the disks are exposed to fluids under pressure are commonly known as "conventional" rupture disks. Conventional rupture disks are placed in tension by the force of the fluids under pressure exerted thereon and rupture occurs when the tensile strength of the disk material is exceeded. Rupture disks including concave-convex central portions in which the convex side of the disk is exposed to fluid pressure are known as "reverse buckling" disks. Reverse buckling disks are placed in compression by the fluid pressure and, typically, the concave-convex portion first reverses itself and then ruptures when an overpressure condition occurs.
Knife blades have been utilized with reverse buckling rupture disks to puncture the disks upon reversal and bring about the full opening thereof. Scores or grooves have been utilized in both conventional and reverse buckling rupture disks to create lines of weakness along which the disk ruptures when overpressured.
While the various prior rupture disk assemblies have been successfully used in a large number of applications, problems are still encountered. One such problem is fragmentation of the rupture disk, i.e., pieces of the rupture disk fragment or sever from the assembly and may contaminate and/or damage the processes and/or equipment into which the fragments are carried. U.S. Pat. No. 5,005,722, which is assigned to the assignee of the present invention and which is incorporated herein by reference for purposes of disclosure, discloses a hinge member which extends into the concavity of a reverse buckling disk in alignment with the mouth or open side of a C-shaped scoreline. When the disk ruptures in the reverse direction, the petal created by the C-shaped scoreline wraps around the hinge. The hinge thereby prevents fragmentation of the petal.
Although the hinge member has been successful in preventing fragmentation of the reverse buckling disk, the hinge member does not work reliably when placed on the convex side of the disk, as would be needed with a "conventional" rupture disk. Also, rupture disk assemblies are easily installed upside down, as most rupture disks and rupture disk assemblies may be installed with either side of the disk oriented towards the fluid pressure source or vessel which the disk is installed to protect. Since, at present, there is no reliable anti-fragmentation device for use on the convex side of a domed rupture disk, if a reverse buckling disk is installed upside down, the system downstream of the rupture disk is exposed to fragments of the rupture disk. Since installing a hinge member on the convex side of the rupture disk has proven to be an unreliable method of preventing fragmentation, simply placing hinge members on each side of a disk is not an acceptable solution to this problem.
Therefore, there is a need for a device which may be placed on the convex side of a rupture disk to prevent fragmentation when the rupture disk bursts in the conventional direction. There is also a need for apparatus and method for preventing fragmentation of a rupture disk which may be placed on both sides of the rupture disk in order to prevent fragmentation whether the assembly is installed in the proper direction or upside down. There is also a need for such an apparatus which is easily installed and which may be retrofit to rupture disk assemblies in operating facilities.